emphysema

Pronunciation: em'fi-se'ma

Definition:

Presence of air in the interstices of the connective tissue of a part.

A condition of the lung characterized by increase beyond the normal in the size of air spaces distal to the terminal bronchiole (those parts containing alveoli), with destructive changes in their walls and reduction in their number. Clinical manifestation is breathlessness on exertion, due to the combined effect (in varying degrees) of reduction of alveolar surface for gas exchange and collapse of smaller airways with trapping of alveolar gas in expiration; this causes the chest to be held in the position of inspiration (“barrel chest”), with prolonged expiration and increased residual volume. Symptoms of chronic bronchitis often, but not necessarily, coexist. Two structural varieties are panlobular (panacinar) emphysema and centrilobular (centriacinar) emphysema; paracicatricial, paraseptal, and bullous emphysema are also common.